There is a coffee shop in East London’s Brick Lane which proudly displays the sign ‘Come happy, leave edgy’ on the pavement outside its front door. Look at it one way and our society is permeated with establishments vending pleasing pick-me-up drinks to lighten the fatigue of socialising punters. Look at it another and we’re beset by drug pushers dealing a psychostimulant so skilfully disguised that we hardly notice. And in common with other drugs it’s big business: only oil exceeds coffee as a globally traded commodity.
Each cup of coffee contains approximately 100mg of caffeine, each cup of tea 50mg. Caffeine’s mechanism of action is not fully understood but appears to be dose related; it has a stimulating effect on the central nervous system, heart, blood vessels, and kidneys and also acts as a mild diuretic. The positive effects of moderate doses (up to approximately 200-300mg daily) include improved motor performance, decreased fatigue, enhanced sensory activity, and increased alertness.
However it is also recognised that habitual users of caffeine can suffer from symptoms of withdrawal and a dependence syndrome is also described. DSM-IV lists four caffeine-induced psychiatric disorders: caffeine intoxication, caffeine-induced anxiety disorder, caffeine-induced sleep disorder, and caffeine-related disorder not otherwise specified. A 2004 analysis (1) lists the following as attributable effects to caffeine withdrawal, and found that as little as one cup a day of coffee can produce a caffeine addiction:
headache, fatigue, decreased energy/activeness, decreased alertness, drowsiness, decreased contentedness, depressed mood, difficulty concentrating, irritability, and foggy/not clearheaded, flu-like symptoms, nausea/vomiting, and muscle pain/stiffness.
If this doesn’t bother you, another study in 1994 (2) found caffeine withdrawal to carry with it such behaviours as screaming at the children, missing work, going home early, and cancelling a child’s birthday party.
The majority of our intake comes from tea and coffee, but it is also available in energy drinks, food and tablet form. You can see from this list that there is a wide range of caffeine doses. The caffeine content of coffee is well known, but what about that in chocolate or 7-UP? Starbucks coffee comes out top of the ‘caffeine content’ pops, the speculation is that it is not the strong flavour and distinctive aroma (piped into the street) that keeps customers coming back for more, it is – like other addictive drugs – the avoidance of withdrawal effects.
Furthermore, unlike oil or tobacco, caffeine is neither regulated nor taxed. I’ll give Roland Griffiths, professor of psychiatry and neuroscience at Johns Hopkins the last word:
“We need to recognize that caffeine really is a drug and accord it respect as a drug. People need to know what it does when they take it, and what it does when they cease to take it, and make an adult decision about that”.
(1) Juliano, L. M., Griffiths, R. R. (2004) A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features Psychopharmacology 176, Number 1 / October 2004 1-29
(2) Strain, E., Mumford G. K., Silverman, K., Griffiths R.R. (1994) Caffeine dependence syndrome: evidence from case histories and experimental evaluations JAMA 27 1043-8
In the press
I’ve spent how much on coffee? Polly Vernon Observer 23 June 2008
Caffeine related psychiatric disorders – eMedicine